Design patterns·Who calls whom, and when
you changed one field and four other things updated, and finding out which four meant reading a subscription list.
Observer pattern
Also calledobserver, listener, subject and observers
A subject holding a list of dependents and notifying each of them when it changes. It is in-process and direct: the subject holds references to its observers, so the two know about each other in a way publish-subscribe deliberately avoids. Its recurring problems are all lifetime problems — observers that are never unsubscribed keep their subject alive, and notification order is an unwritten dependency people come to rely on.